A U.S. study says obesity increases the risk of prostate cancer recurrence in both black and white men, challenging previous research which suggests obesity may be more significant for black men, according to media reports Monday.

Study senior author Dr. Stephen Freedland, an associate professor of urology and pathology at the Duke University Medical Center Prostate Center, and study author Dr. Jayakrishnan Jayachandran, a urology oncology fellow, examined the medical records of 1,415 prostate cancer patients that had undergone a radical prostatectomy.

It was found that race had no influence on the relationship between obesity and the aggressiveness of the cancer.

Jayachandran pointed in a news release from the school that higher BMI [body-mass index] was associated with significantly increased risk of cancer recurrence for both blacks and whites.

It is still unclear why obesity increases the risk of prostate cancer recurrence, but altered hormone levels might play a role.

"Obesity is associated with more estrogen and less testosterone, and it may be that lower testosterone promotes more aggressive tumors as recent studies have suggested," Jayachandran said.

Other obesity-related changes in the production of hormones, such as insulin, insulin-like growth factor or leptin, may also be involved in the development of more aggressive prostate cancer.

Jayachandran said that they are actively studying all of these factors.

(Agencies via Xinhua August 24, 2009)